1. Cook Morningstar® Farms Grillers Prime® Veggie Burgers according to package directions. Immediately, top each burger with one slice of cheese, if desired. Let stand for 1 minute to allow cheese to melt.
2. Place one lettuce leaf on each bun bottom. Top with burgers, pickles, tomato slices, onion rings and bun tops. Serve with ketchup and mustard, if desired.